Ok, here's the deal. I've been reading post after post about what size injectors on a 350 and some say 21#, some say 22#, and yet others say 24#. So here's what I have.

-355 TPI 360 to 375 HP (at the flywheel)
-TPI Ported and Polished
-SLP Runners
-Hi Flow Intake
-Hypertech Thermomast chip for a 350
-Hypertech Rotor and Coil Kit for dist.
-AFPR set at 42 psi w/ vacuum on 47 psi w/out vacuum
-K&N airfilters with the modified air boxes

I have all the other 305 to 350 swap parts installed so the only thing I have left are the injectors. With what I have, what would be the best size injectors? Also, what brand is everybody running?

Id go with 24lbs injectors jegs sells the accel's for $229.99 whitch I think is a good price

you could also go with 21lbs injectors so you could use any aftermarket 350 chip the 24lbs would need a custom chip

jegs also has the 21lbs for the same price

Or you could do what i am doing. I just bought 24# accels from summit and compensate the bigger injectors with a AFPR. Gonna do it that way till i can send my chip back out to be reburnt.

Get 30#'s.... 24#'s are too small for the power you think you will be making... here is the formula

HP= Injector x 2 x #cylinders x %DC (Duty Cycle)

you should never exceed 90%DC and should keep the max around 80-85%


Hope this helps ya

The 24s will be fine. They work in supercharged LT1s up to 450 at the crank so I can't see you hurting them with your power level. I ran them in my wifes car before we started making more power. Save your money and run the 24s.
Ed Wright advised me to NOT buy accels. According to him the accels vary up to 25% on their advertised flow rates and he has had several cars on his dyno exhibit this problem.

I have a better guestion, how are you going to tune things to optimise what you've installed?.

On the DIY-PROM board there are some stickies about this. But, in short if you want to run a stock ecm, and you want to double the HP, then you might well consider running 2x as large of injector.

The alledged problem with the big injectors in that you actually have to put some time into figuring things out rather then actually developing a fuel curve. With the small injector train of thought they just run the injector static, or always on at WOT, and then call it quits. So the aftermarket, and those that are more interested in quick and easy go that route.

The early, ie late 80s injectors did have some minor issues, but the newer stuff has been fine from what I've seen. Some get a bad wrap since at smaller pulse widths they're not too linear, and that just means having to work a little more on the tune.

Too large of injector means, maybe fouling a plug while your getting it tuned, too small of injector means maybe a hole in a piston.

Goggling will turn up lots of info on sizing, and RC Engineering has a lenghty page about it.

Grumpy,

I have thought about getting into PROM burning, but right now I don't have the time or the money. So right now, I'm pretty much looking for the quick and easy way out I read through a couple of those stickies and it's all greek to me. My problem now is that I'm running 19lb injectors that are a causing a light ping due to lack of fuel. I've adjusted my fuel pressure back and forth a nothing really helps. My hope is that with the amount of air I'm pulling in, I'm going to need to balance it with more fuel, so my thinking was bigger injectors. And I know I do run a little lean according to my A/F Ratio Guage, so maybe injectors would balance that too.

How would I go about doing this? Are you turning the pressure up or down?